Power-reverse gear



F. w. MARTIN IfOWER REVERSE GEAR Oct. 30, 1928.

Filed Jan. 2'7, 1925 INVEN TOR By W z/W/w;

smaw A TTORNE Y5 Patented Oct. 30, 1928.

UNITED STATES PATENT OFFICE.

FREDERICK W. MARTIN, OF BROOKLYN, NEW YORK, ASSIGNOB T FRANKLIN RAIL- WAY SUPILY COMPANY, A CQRPORATION OF DELAWARE.

rownn-nnvnnsn GEAR.

Application filed January 27, 1925.

This invention relates to-power reverse I gears of the servo-motor type and is especially useful forlocomotives.

One of the primary objects ofthe invention is to provide a simple and effective form of gear constituting an improvement over the type of gear shown in the Roberts Patout No. 1,500,685. The gear of my invention is directed to obtaining the same general advantages as the gear of such patent, but by the improvements now to be described.

The foregoing,.together with such other objects and advantages as may hereinafter appear, or are incident to my invention. I obtain by means of a construction which I have illustrated in the first form in the ac 1 companying drawing,'wherein the figure is a fragmentary longitudinal section through the gearillustrating my improvements.

1 Referring now to the drawings, the gear comprisesa cylinder 7, in which there is a piston 8, having a hollow rod or extension 9 which may be connected to the link motion by a reach rod of suitable character (not shown) the valve 10 for controlling the admission to and exhaust of pressure from the cylinder on opposite sides of thepiston; and

- 11 has a suitable packing 13 in the cylindrical portion 1 1 of the cylinder head 15. At a point adjacent the valve 10 the sleeve 11 has two spaced annular shoulders 16 between which the conneoting'member 17 is swiveled. This member 17 has a tongue fittingwithin the recess 18 formed in the valve 10. By this arrangement the sleeve 11 may be rotated, relative to the connecting member 17, but when the sleeve shifts longitudinally such connecting member is shifted longitudinally so as to impart corresponding longitudinal movement to the slide valve 10.

The sleeve 11 i is rotatably but slidingly connectedto the rod 19 at its inner end 20 1 itbeing limited in its sliding movement in Serial No. 5,038.

either direction by the abutments 21-21. The abutments are spaced a sufficient distance apart to allow full opening of the valve 10 in either direction. In this connection it is to be noted that the rod 19 is fixed against longitudinal movement bymeans of the fixed member 22 engaging the groove 23 in the rod adjacent the cylinder head 15. Thus it will be seen that the sleeve 11 is given rotary movementby virtue of its keyed or splined connection with the rod 19 as indicated at 20 and longitudinal movement by virtue of its screw threaded engagement with the piston rod 9. Suitable shafting and coupling means connects the rod 19110 an operating hand wheel in the cab of the locomotive.

Reverting now to the valve mechanism it will be seen that the valve 10 is shown in neutral position and that the length of the valve is such that it cannot at the same time cover the port 24 communicating with the forward end of the reverse cylinder and the port 25 communicating with the rear end of the cylinder. There isa positive lap of the valve for exhaust pressure, the amount of which with reference to the negative lap is such that when either port is ust cracked open exhaust does not take place, or stated in another way, either of the inlet ports may be just closed without exhaust taking place. The operation of the gear is as follows. The parts as shown in the drawing are in neutral or mid gear position and if it is desired to move forwardly the shaft 19, under control of the hand wheel in the cab is rotated in a clockwise direction, which causes the sleeve 11 with its connecting member 17 to move toward the rear, the piston 8 acting as a nut, such rearward movement being imparted to the valve 10 which uncovers the port 25 to admit pressure to the rear of the piston. Upon such movement of the valve the port 2 1- is connected with the exhaust port 27 through the medium of the groove 28 in the under side of the valve, to exhaust pressure from the other or for ward end of the cylinder. The limit of pos sible movement of the valve 10 is determined by the stops 29 which are engaged by the annular shoulders 16 on the sleeve 11.

The pressure admittedto the rear of the piston normally would cause it to move forwardly carrying with it the sleeve, connecting member 17 and valve 10, bringing the valve to substantially middle position as will further appear; .However as long as the shaft 19 is being rotated rapidly enough, the valve will be held in its extreme left position, notwithstanding the forward movement of the-piston," Continued rotation of the shaft 19 will bring the piston to full forward position of cut off, corresponding to the corner in the usual reverse lever m'ech' anism. Upon cessation ,of ,rotative movement of the shaft the piston carries the sleeve andofialve to, substantially middle position, cutting off. the admission of full application of pressure bnt leaving bleed pressure. i v 1 Since ,the'load onthe piston is normally in a forward direction, inactual operation the parts. come atrest with the port 25 just covered and with the port 242 just cracked (forQpurposes of illustration. the negative laphas been considerably exaggerated in the drawings). Reservoir pressure bleeds to the forward end of the cylinder maintaining a pressure sufficiently in excess-of that in the rean end of the cylinder .to compensate for the diiference in the areasof the piston faces and the forward pull on the piston. mile the device may pump, it Will only do so occasionally for the reason that it takes considerabletimeto build up enough pressure to causei the piston to move rearwardly owing to friction, the difl'erencein area, the pullcn. the piston, leakage and the factthat although the" port 24 .is cracked no exhaust takes place through port 25. I-Iowever if the piston is moved rearwardly port 24 is covered and port 25 is cracked without exhaust through port 24:. and .the pressure. is built up on therear, side ofthe piston to return it to itsfselected position of. cut oil. L pase of more marked movement of the piston admission to and exhaustfrom the cylinder occurs to-produce, stabilizing conditions. w The operation fol-rearward movement is very similar except that the rod 19 is moved counter-clockwise and the ,exhaust takes place through {the groove 30 and exhaust 1 Qrt i In the event of an, .air failure or ifv the locomotive is inaround' house with no air on, it is impossible. for the piston to shift beyond the ,limits determined by the stops 29. Thus for ,exampleina round house, it is impossible for the'gear to creep, as .is the case 'in' some gears, tothe point where re verse, will take place ,and when if air is turned on the'lo'comotive might lback through the wall of the roundhouse as has, occurred.

Iclaimi .I 1 In a servo-motor power reverse gear, a cylinder, a, piston having a hollow internally threaded. m ta, controlling valve, and ,an

operative connection between valve and piston comprising a rotatable sleeve having a head having threaded engagement with the rod and a rod extending through the sleeve and keyed to the head for turning the sleeve.

2. Ina power reverse gear of the servomotor type the combination of a cylinder, a piston having a threaded red, a control valve and means for operating the valve comprising a' rotatable sleeve having threaded engagement with the'piston rod, a rod eXtending into said sleeve for transmitting said rotarymovcment, and a connection'between said slceveuand' the valve.

3. In a power reverse gear of theservomotor type the combination of a cylinder, a piston hazving a threaded rod, a control valve and means for operating the valveconrpris ing a rotatable sleeve having threaded engagement with the piston rod, arod extending intosaid sleeve for transmitting said rotary movement, and a' connection between said sleeve and the valve, the last mentioned rod. being heldagainst longitudinal movement and having sliding connection with the sleeve. 7 i r L-In a power reverse gear of the servomotor type the combination of a cylinder, a piston havinga threaded rod, a control valve and means. for operating the valve comprising a rotatable sleeve having threaded engagement with the' piston rod, a rodextending intosaid sleeve for transmitting said rotary movement, and a connection between said sleeve and the valve said connection being swivelled on the sleeve.

5.In a power reverse gear of the servomotor type-the conibination of a cylinder, a piston having a threaded rod, a control valve and meansfor operating the valve compris ing a frota-table sleeve having threaded engagement with the piston'rod, a rod extending intosaid sleeve for transn'iitting said rotary movement, a connection between said sleeve and the valve and stop means limiting the sleeve against unintended movement.

16. Ina power-reverse gear of the servomotor type the combination of a cylinder, a piston having a threaded rod, a control valveandnneans for operating the valve comprising a rotatable sleeve having a threaded head at its inner end for threaded engagement with the piston rod, :1. rod extending into said sleeve for transmitting said-rotary movement, andwa connection between said sleeve and thevalve.

'Z. In a power reve'rsezgear of the servomotor type theoombination of a cylinder, a piston having an internally; threaded extension,-a control valve and means foroperating the valve comprising arotatable sleeve havingthreaded engagement with the piston extension, a. rod extending through said sleeve and havingwnon-rotative but sliding connection therewith for transmitting said rotatable sleeve having threaded engagerotary movement and a connection between ment with the rod and means for turnsaid sleeve and the valve. ing the sleeve, said means extending through 1 8. In a servo-motor power reverse gear, a the sleeve. 5 cylinder, a piston having a threaded rod, a In testimony whereof, I have hereunto controlling valve, and an operative connecsigned my name. tion between valve and piston comprising a FREDERICK W. MARTIN. 

